Field of the Invention
The present invention relates to a polymer nanofiber structural body and a method of producing the structural body.
Description of the Related Art
Industrial utilization of fine particles has become active. In the meantime, an apparatus for collecting fine particles scattered in air or dispersed in a liquid has been needed. In recent years, a polymer nanofiber structural body in which polymer nanofibers are integrated and three-dimensionally intertwined with each other typified by a polymer nanofiber sheet has been attracting attention as a material for the collection.
Unlike general fibers to be used in a nonwoven fabric and the like, each of the polymer nanofibers has a diameter of several microns or less. Accordingly, the polymer nanofiber structural body is drastically superior to a structural body including the general fibers because of the following reason. Even when the polymer nanofibers are integrated, an enormous specific surface area, a nanosize continuous pore structure, and a low density are obtained. By virtue of those properties, new functions such as a mechanical strength, reactivity, electrical and optical characteristics, and the permeability of the inside of the structural body can be imparted. In particular, when the pore structure is utilized, a pore diameter of the order of submicrons is obtained and hence the pore structure is suitable for the collection of fine particles. Further, each of the polymer nanofibers uses an organic compound as a parent material and hence is lightweight. In addition, the polymer nanofibers can be produced with ease and at a low cost.
Meanwhile, in order to selectively collect fine particles having different sizes, it has been necessary that the polymer nanofiber structural body have a plurality of pore structures therein. In each of Japanese Patent Application Laid-Open No. 2012-223254 and Japanese Patent Application Laid-Open No. 2012-219384, an attempt has been made to bond a plurality of fiber layers to provide a polymer nanofiber structural body with a plurality of pore structures.